John Deere QAS 70 troubleshooting: 15 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
John Deere QAS 70 — full specs, parts & maintenance.
| Symptom | Cause | Remedy |
|---|---|---|
| Alternator gives 0 Volt | Blown fuse. | Replace fuse. |
| No residual voltage | Excite the alternator by applying a 12V battery voltage with a 30 W resistor in series on the + and - terminals of the electronic regulator, respecting the polarities. | |
| After being excited the alternator still gives 0 Volt | Connections are interrupted. | Check connection cables, measure winding resistances and compare with values mentioned in the alternator manual. |
| Low voltage at no load | Voltage potentiometer out of setting. | Reset voltage. |
| Intervention of protection | Check frequency/voltage regulator. | |
| Winding failure | Check windings. | |
| High voltage at no load | Voltage potentiometer out of setting. | Reset voltage. |
| Failed regulator | Substitute regulator. | |
| Lower than rated voltage at load | Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Intervention by protection | Check frequency/voltage regulator. | |
| Current too high, power factor lower than 0.8; speed lower than 10% of rated speed | Failed regulator. | Substitute regulator. |
| Rotating bridge failure | Check diodes, disconnect cables. | |
| Higher than rated voltage at load | Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Unstable voltage | Speed variation in engine. | Check regularity of rotation. |
| Regulator out of setting | Regulate stability of regulator by acting on STABILITY potentiometer. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Blown fuse.. See the table for the matching fixes.
Documented causes: Connections are interrupted.. See the table for the matching fixes.
Documented causes: Voltage potentiometer out of setting.. See the table for the matching fixes.